Dang, Alex. You just blew my mind. The roof example explained it really well, and proved to me that I was wrong. We put out a sharpeners video earlier this year, and I took part in perpetuating the myth, saying that if your edge didn't fall along the perfect radius of the circle drawn by the sharpener, then you'd get uneven edges. The knife we sharpened for the demonstration did get uneven edges, but your video explained that nicely. I think another thing I learned here is that, in addition to the knife maintaining the same edge along a straight line, the "perfect radius" thing I talked about in the sharpeners video also applies. So if you have a drop point that goes behind the "roof line" you showed us, the stone can still turn and give you a perfect angle along its radius. As always, I learn a lot from your videos. Thanks for making them, and making all us knife nerds a little smarter every day. I hope to be proven wrong by many of your videos in the future! -George
I can't remember where i read the roof explanation, I think it was on a forum a long time ago, but that was the moment I realized, I was thinking about the angle from the wrong direction. It blew my mind when I heard it as well👍
@@OUTDOORS55You and Neeves are elevating the video standard on RUclips for knife sharpening videos. Before you two, this information was out there but it was really scattered and hard to piece together. I’ve really enjoyed being able to learn from the content that you two produce, which has enabled me to help my friends learn how to sharpen as well.
@@OUTDOORS55 I remember where you possibly saw it. It was a RUclips post by a knife maker who was sent a knife sharpener by the company to review it. And he gave the roof profile to explain the bevel angles. It was well before Covid so a fair while ago.
people love seeing professionals at work or just in general people in flow states. I also think that we as men just love getting shit right and appreciate a well explained deep dive into any sort of matter🤔
@@snowhusk Knives are also one of those hobbies full of old wife's tales which are repeated as fact. It's nice to see someone back up their claims with evidence, and refute the parroted misinformation.
@@JMMC1005 yup, totally agree with you! It's funny how even deep in the weeds we can still retain some of those myths, like with the topic of this video And we've got a great community for that! This channel and Jerad from Neeves Knives are great for sharpening information (I still refer people to Jerad's video on pull-through sharpeners to explain why those don't work and why you wouldn't want them) and Pete from Cedric Ada is great for comparative tests and general no-bs view on knives (I studied his results of different steels' cut tests when I was getting back into the hobby, and now my daily drivers are either D2 or 14c28n, couldn't be happier on a budget and it's great to know exactly in which ways and how they are different to 8cr13mov, the defacto pocket knife budget steel for the original time period when I was into knives)
Nice explanation. When I saw your roof setup, I realized that I hadn't taken into account that the sharpening stone rotates so that it is always contacting the knife edge at the roof angle, not the rod angle.
Great explanation. I'm a mathematician, and I incorrectly assumed the angle was changing on long knives when I was using a fixed angle sharpener. The visual with the roof was brilliant. I didn't need to see any more to realize my mistake.
"the only place these angle finders are accurate is when the guide rod is perfectly aligned with the center of the knife sharpener" I NEEDED TO HEAR THIS! 😅 Thank you. 🍻🙌
Thanks. As a retired engineer and (manual) draftsman, ia am well aware of the angles, however you have provided me with another way to attempt to explain this to laymen. Now, back to my Laskey sharpener.
Mechanical Drafting is unfortunately soon to be a lost art/skill, at least in the field of architecture and similar design type fields of work. There was a really good article written a while ago by Michael Graves regarding how much the design field in total is going to suffer and things will become more and more sterile and similar looking as technology advances & it explains why so many commercial buildings are absolutely unremarkable while buildings designed 50-100 yrs ago have an inexplicable sense of character and beauty.
Did you explain that it is sweeping a conical surface and not a planar one, but that it doesn't matter? If not, then they are right and you are wrong... just not in any practical way. What do I mean? Sweep the device 360 degree. Now tell me if you just defined a plane? The answer is no. You instead defined a cone.
With a curved blade, so long as you clamp it at the same place each time, you’ll get the same angle at each point of the blade from sharpening to sharpening. That consistency is more important than the exact angle.
Visually it can be an issue though, almost all of my knife has a noticeably larger edge than the belly. Personally I do like the look but can see people would like a crisp, even edge
True. It will still have a slight difference in edge angles depending on how curved the blade is but realistically, those differences would be quite small and be inconsequential. What you can do (and what i did at the beginning) is just draw a square along the clamp's edge on the blade for the first side so that when you flip it over, you can clamp it in the same spot. That's if it's one of the types that don't rotate 360 degrees and you need to remove the blade and flip it yourself, if not then there's no need for that.
Thanks for going over this. I started out with a fixed-angle sharpener from WorkSharp and have been wracking my brain over this "problem" since. I, too, am five years old.
The key takeaway here is that angle does change when there is a curvature, the difference on a fixed angle is so minimal, your free hand technique willdprobably deviate more. I have been using free hand and fixed angles for years and only use fixed for my expensive kitchen knives, it just gives so much control over the actual angle and never get any scratches. I mainly have 240mm japanese kitchen knives and both Shapton as Naniwa stones are available for these systems. Free hand sharpening is just more satisfying and gives you a more DIY achievement feeling.
This is a good plan for when I start a chef knife collection. But I 100% agree that free hand is extremely satisfying and relaxing with the proper mindset. Some people meditate, I free hand sharpen.
I have nice Japanese kitchen knives that I freehand sharpen-now that I’m good enough at sharpening that I don’t dull them instead. The sharpening itself is satisfying but using a really sharp and really well-made blade is true bliss. 😊
In my experience with a similar system, there was a difference in angle toward the curved tip, but not enough to be problematic on the blades I tested with. The system I used was much smaller, meant to be portable. The longer the swing arm is (further the pivot point) the less of a difference in the angle as the blade curves. So if it's a concern for you, buy a system with a long swing arm.
There have been some videos from others that have countered his arguments on more than one occasion. I'm just saying, no ones always right. And I still enjoy watching him even so.
Great explanation! My old buddy Ken Schwartz tried to explain this to people for many years and a lot of folks just don't get it. Our intuition is not reliable sometimes, and we need to try many methods to learn until we find one that clicks.
@@OUTDOORS55 But is there any technique you can use to minimize angle change when targeting the curve, or is it something we just have to live with? Sounds like it might be better to clamp your knife closer to the tip/belly instead of right in the middle? Does twisting/rotating the rod do anything when approaching the belly? Still so many questions! Thanks for the great video, as always!
@@xyrojin89 It's the perpendicular distance between the guide rod support and the blade edge that matters. The easiest workaround would be to do the blade in sections, reclamping to get the distance consistent as you go.
@@xyrojin89 Like JMMC1005 said; do the knife in (small) sections and confirm that the distance from the edge to the base of the vertical rod-support remains the same. You can also mitigate the difference by clamping the knife in such a way that the edge is as far away from the vertical as you dare (minimal spine between the clamps). Or by extending the distance between the clamp and the base of the vertical rod-support. Your clamp and the rod-support don't have to be in one piece like with all these sharpeners. You can clamp the vertical rod-support to a workbench and clamp the knife at the edge of the workbench. Now you are only limited by the length of your rod (which you can always extend). By increasing this distance, you decrease the difference in angle. Example: if your knife is 5 wide at the belly but only 4 at the heel & tip. Sharpening it with a 10 distance (between spine and vertical) means: The belly get sharpened at ( 10 + 5 ) = 15 distance, while the heel & tip get sharpened at 14 distance. This is a difference of about 7% If you extend the rod and place the vertical support farther away, say at 100, the numbers become: Belly ( 100 + 5 ) = 105 versus ( 100 + 4) = 104 for the heel & tip. Now the difference is less than 1%. So you would go from a 7% difference in angle along the blade to a 'less than 1%' difference in angle !
Beautifully illustrated. Especially when you used the digital angle finder and reminded us that it has to be perpendicular to the blade in order to be accurate. Very nicely done.
Literally just bought a KME and the same Klein angle cube you used in this video. Couldn’t figure out for the life of me why the cube was showing different angles depending on the position of the guide rod. It’s like you read my mind and made the exact video I needed, thank you!
I havent used fixed angle systems yet. I'm still enjoying free hand quite a bit but I'm sure I'll get some fixed system eventually and when I do I'm sure I'll come back to this video. As always thanks for the great content.
Thanks for explaining this. As a side note I just got a sharpall 300/1200 stone to sharpen my kitchen knives which have been very poorly treated. I had been using a pull through sharpener but wasn’t really happy with the results. I have now dropped myself in to the deep end and doing free hand sharpening. I have to say you make it look very easy. I just want to point out how much skill you have, that you can pass on the information and techniques in a way that makes it seem very accessible , but it is definitely a skill that requires time and repetition to get good results and your videos are a great foundation for helping others work to getting good results
Hang in there! I now have about 20 sharpenings under my belt with the Sharpal (the last two or three, with a leather strop and 1 micron gunnyjuice) I am still not getting "hair shaving" edges. But my knives are all much sharper than they were before. And I was able to get them sharp enough to make a very noticeable difference in use almost immediately.
The reason I quit using fixed clamp systems was exactly what you mentioned about getting fat bevels at the tip. I've got a lot of older knives that were sharp but had really ugly, wide tip bevels that I've fixed on the worksharp KO grinder or freehand. Great explanation.
Thanks for this. I have been through a lot of math classes and the like in my life, and I would have thought the angle changed. Amazing way of proving me wrong! Thanks again.
I believe some (not all) curves will work as well. For example, a centered, perfect circle should work! I _think_ it's just this needs to be satisfied: d * cos(x) = r Where r is basically the clamp arm's length, d is the distance from the tower to the point of the blade that's being sharpened, and x is an angle of _misalignment_ between the rod's angle and the blade's "cutting direction" at that point (which is 90 degrees from the edge direction). All of this is 2D, ignoring height (imagine a top-down view) None of these curves are arcs of circle, except for one with radius exactly r, so there are constraints here. But I believe this may let you get some reflex curves (think karambit). So it depends on the rod's pivot angle, rotation, and extension, plus the _edge's tangent at a particular point._ A _perfectly circular blade centered on the pivot axis_ (or any arc of this circle) is a special case where neither d nor x are changing. If you break up x so that x = y - t where y is the rod's angle and t is the cutting direction angle, then a straight blade would be a "special case" where t never changes, only d and y. But other constant-angle curves are possible as long as you adjust d and x (or d, y, and t) such that the changes in one cancel out changes in the other(s).
With this, even tantos could be positioned so that both edges could be sharpened to the same angle if you wanted to do that, but you'd have to position the tanto exactly correctly. The main edge would be mounted like normal, but you'd have to slide it to the left/right enough so that the line of the secondary edge, if extended, would be tangent to that imaginary circle. Basically, if you put the rod over the heel where the two edge meet, it'd need to exactly bisect it its angle; the two sides would be reflections of each other (across the rod). This is because there are two ways for the rod angle and cutting direction to be off by x degrees -- clockwise, or counter-clockwise. So every point in space actually has two solutions (except the circle itself, which only has one everywhere on its edge. And I guess its very center). Another way of saying that is that cos(x) = y has two solutions for x: acos(r), and -acos(y). So when designing an edge, you can continuously choose the angle that takes you away from the circle, until some point, then switch to choosing the angle which takes you towards the circle, and it can still maintain a constant angle the whole way. If the initial edge is straight, then this will result in tanto-like blades. For other angles/curves, both parts would be curved, but there's be a discontinuity at some point. Again, each side of the discontinuity would be a reflection of each other. Also, although points exactly on the circle only have one solution, they have many possible "next" solutions. So you could have one side of the clamped point be one curve and the other side be another, breaking symmetry at that point. For points inside the circle, going "away" from the circle means going to the center. Swapping to curve back towards the circle again would create another kind of "reflex" edge with a discontinuity inside it. "Normal" reflex edges might be possible by going to points further than needed for a straight line.
Excellent demonstration! The idea of looking at the sharpening stone on its slider from the side is very convincing. The demo with your roof model is even better. In other words: The angle that matters is the bevel measured perpendicular to the edge. I love your idea of using a 'roof' model! BTW - in the demo of how blade sweep affects the angle, you rotated the sketch board in the wrong plane. A swept edge would remain in the same plane as the 'roof'. But, I understand what you were trying to say.
No it was the correct direction. The angle on the "sweep" changes based on blade length. Since the sweep rotates the angle to the angle of the guide rod, which changes based on length from the center. I just scratched the surface here and its hard to visualize haha
That makes a lot of sense. Longer kitchen knives still pose a problem with my kme because of the curved tip. The bevel there teens to always be bigger than on the straight portion of the blade.
I've been trying to explain this to people for a long freaking time. The angle doesn't change until you come around a corner on a fixed angle system, like this. I've always used a "self healing mat' under the base of the sharpener. I line up the back of the sharpeners base to a horizontal line & when I clamp a blade in, I make sure the majority of the straight portion of the blade edge is centered to the guide bar & even with a line on the mat. To me, this helps ensure that at least the straight part of the blade has an even bevel. The belly will always be at a higher angle, depending on how far it curves back towards the vertical plate that the guide bar is mounted in. THAT is the angle/area that is causing some FUBAR in peoples' minds, I think. That, and what you showed, the angle finder has to be perpendicular to the angle guide mounting plate for accuracy. That's how I perceived these fixed angle sharpeners working. Education may help but just having a mechanical mind, a love of how things work & working with your hands is what 'figured' this out for me. Me, a guy with a grade 10 education & 146 IQ. (had to get tested for a job placement, job) I asked, "is that good?" lol Thanks for the video & insight! Loved it. Cheers
I'm glad you mentioned that angle can change with curved blades. To make it clear, If axis of the radius of the edge goes exactly through the heim joint of the sharpener, angle will not change. If that axis is behind the heim joint (big radius) angle will get lower as you go away from the center. If axis is between the edge and heim joint (agressive curve) angle will get higher as you go away from the center.
Seems like the ability for the rod and stone to rotate freely in addition to pivoting and extending is key here. I hadn't considered that before, and because of that I had thought the angle wouldn't be consistent. In fact, that extra degree of freedom makes me wonder if it might also give relatively consistent angles even for curved blades? Before you showed me this I thought it could only be consistent for a perfect circle centered on the pivoting axis (which would also imply the rod would never need to extend or retract). And without rotation I think that would be true. With rotation I think any shape between that circle and perfectly straight could work, i.e. a curve that's gentler than the circle would work, up to and including it being so "gentle" it's actually straight. A curve that's _tighter_ than that corresponding circle couldn't be perfectly consistent, but might at least be closer than you would expect. I don't think a reflex curve would be any better though. Edit: Eh, I don't think just _any_ curve between the two would work, even if you considered local curvature. In the tanto scenario the tip area's edge is straight but could be farther away, which would be a different angle. Either perfectly straight and perfectly circular are the only optima, or else for every point between the two there's a unique blade direction that would work, but I'm not sure how you'd find it. Curves might still be a little closer to consistent then you'd naively expect though. Edit 2: Maybe every circle larger than one centered on the pivot axis, positioned so the center is directly behind/in-line with the pivot axis and clamp would work. So any arc of a blade that follows the edge of one of these circles would work. If you position a blade to take advantage of this you'd get better consistency than otherwise. Maybe.
One way to visualise it is to look at the rod from the side, along the blade. That way you can see that the angle does not change as long as the blade edge is straight.
I will add this comment as a yes and... Long comment comming here. Sorry. 1. The knife edge has to be perfectly centered to the center line of the clamp or the angle of the stone to the edge will change back and forth every time you switch sides of the blade by rotating it. This has definitely been one of the more distinct challenges for me using the kme system but it will also reveal that not every Factory sends their knives out with a perfectly symmetrical on both sides of their knives. Cold Steel specifically has been pretty bad about this for me. To the point that some of their edges I.'d almost qualify as a chisel ground. 2. Because the KME uses and easily ratating single clamp the and because of the rubber lining of boot on the inside of the clamp, the firther from the center of the the clamp line the clamp. It os fairly easy to flex the out of alingment on both the rotating alignment and the clamp Center Line alignment. This is why it is very important to both have the clamp locked down very tight and the rotation set to a fairly tight lock in well. The more pressure added from the stone the easier it is to flex the knife. I used the term because it dosent so much shift because after the preasure is lifted it will retirn to where you had it set. 3. The actual number of the angle matter for f*** all in except to give you an idea of how thin or thick your edge will be. 4. The height/broadness of the blade (spine to edge) will effect the angle from one knife to the next if the angle height is unadjusted. 5. Running a fealty along the edge is the best method for checking that you are getting a good surface contact between the stone and the edge bevel. It is also good to recheck that you are continuing to get that perfect match throughout your sharpening. I have had it where I had everything perfectly aligned at the beginning of a sharpening session and then by the end I had pushed or changed the angle by over pressuring one side or the other of the knife in the clamp and it shifted. This left it so that I was too steep on one side and two shallow on the reverse. 6. I do think that the bigger the system the easier it is to sharpen across the entire Edge and look forward to getting the larger KME at some time in the future.
That's somewhat clearer. The 'roof angle' analogy is helpful. But then the belly and sweep muddied the waters. As a kitchen knife user and sharpener almost all our knives have bellies and sweeps.
You can just put your angle finder to the rod, move that rod to the end of the blade, and tun the angle finder to make it perpendicular to the blade to see the angle is the same. Maybe add small platform to the rod to make your demonstration simple.
I have owned this style sharpener for years now and LOVE it. I had this discussion with a co-worker because everyone is a knife sharpening expert. I think i need to draw it in CAD properly to show the sharpening angle. I did a basic one ages ago but mesured rod angle, it roughly shown a 2° change over a 6" blade centred in the clamp. But as you have shown, the stone rotates, and the sharpening angle is not the same as the rod angle. With this system i only sharpen my 2x kitchen knifes once a year. No matience during that year only the sharpening
You can apply the roof argument to a circular blade when you think of the roof as a cone with the pivot on its tip. Feels paradoxical until you really think about it.
That’s a good observation. You could sharpen a disc with a consistent angle all around if you put the pivot point on top of the center of the disc. The straight roof becomes a traffic cone when you follow a positive curve.
so if you projected the triangle made by the sharpening arm onto a plane that was prependicular to the blade at any point it would be the same triangle. so the sharpening angle is the same at any point on a straight blade any distance from the pivot, but the sharpening angle changes if the blade curves?
I was like "omg, the angle DOES CHANGE there aint NO way he can explain that" Preceeds to do exactly that I cant remember being mind blown like this since the Monty Hall problem
Thanks for the roof analogy. It really helps to understand. To make it even more visual, you could attach a small laser pointer to the back end of the rod and project the beam onto a sheet or screen. When you sharpen the blade along its straight parts, the laser beam will follow a straight trajectory on the screen and along the curved parts of the blade, the beam will also have a curved trajectory.
Yeah, we imagine the angle in a 2D simplification and apply 2D knowledge of trigonometry to a 3D problem. The roof is an excellent non mathematical explanation! Good work!
This is a cool example of trying to apply a 3rd dimension to a 2D object. The reverse is also easy to demonstrate. The sharpener can be lifted and exist in a higher dimension than the plane. Adding curves makes more sense to our intuitive understanding of the world, where straight objects are always artificial.
This is the nice thing about free hand sharpening. If I ever feel I'm too shallow or too steep it's a pretty easy adjustment. It's relatively easy to adjust a mechanical sharpener too but it's hard to beat the convenience of your hands.
good demonstration, just wondering if there is any noticeable difference with edge retention on these fix angles sharpened knifes. I'm thinking the micro abrasion angles might not be diagonal with the edge. for example it looked like in your last video between 7-8 minutes you sharpened the knife near the center of the guide rod. It looks like there were times you are moving the stone perpendicular to the blade. Does that affect the edge in any way, or does the strop afterwards fix that if it does?
Wow this is the best explanation of how this works. The simplicity which you have put this blows my mind. I knew that was a myth but I didn't have a good simple way of explaining it. Thank you
Great video and explanation Alex. Another way of visualising this is to place a light source at either end of the knife blade with the the light facing the sharpener side on. Turn of all other lights and project the shadow of the sharpening stone/arm on a wall. No matter where it is on the (straight) blade, the shadow will always show the same angle as you had set.
This is so much more simplified than I could have explained it and to try and explain it with maths we would have an hour long video, and half the viewers falling asleep during it bring back memories of college days
Excellent....I did have a "Ha Ha" moment. Thanks. So what's your advice to novice knife sharpeners like me...use a fixed angle sharpener or learn to do it freehand?
At first i was worried that you misunderstood the problem, until you showed the "exception". (And i am really happy, because you explained the angle change there in a very visual way.) But, in my opinion, the word exception is probably not the perfect fit, as most blades have a curve towards the tip. I don't have a single one that is comppletely straight, or has little to no belly towards the tip. More the opposite. For example, if you look at a Kabar or a Glock field knife, and clamp it at close to the grip, the angle change is noticable with your eye. As like you mentioned, the bevel you create with the sharpening system widens. But if you clamp it closer to the tip, you can avoid thining out the tip.
I think the ”problem” people have is what you explain at 06:58 They see a difference in edge width and assume the angle has changed. It’s the ‘lifting the elbow’ part on whetstones.
The angle changes only if the distance from the contact point of the stone to the knife to the pivot point gets closer. ie carve blade. easy way to tell is when the guide rod upwards or downwards. if you are sharpening a kukri for example. Thank you for taking time to explain this. I have never seen a youtuber explaining this. i busted my brain thinking about this conundrum.
Great explaination, brain bender to imagine the contraints for wich fixed angle sharpeners keep blade angle constant. They clearly work with both straight knives and knifes with curvature where the sharpener pivot point is the center of curvature, probable also curvatures intermediate to this. However not knives where the curvature changes. so you will not be able to sharpen a kopesh on fixed angle sharpeners
I knew when you posted the last video that inevitably this follow-up would be coming. It's crazy to me how many people needed to be spoon fed this. Doesn't seem that complex. I've noticed in most fixed angle sharpeners, if the angle is changing much on longer blades, it's usually do to clamp rotation, or some other critical tolerance failing when you need it. Great follow up vid my mans.
It is a compound angle. There are two angles on two planes. The X Y plane and the ZY plane. The angle on the XY plane may change but it is the ZY angle that does not and that is the angle that is sharpening the blade. If you placed your camera parallel to the blade you can see the angle does not change and if you hold the angle meter perpendicular to the blade while the rod moved it should have stayed the same
Yes, if you treat it as vectors and resolve them to the plane of the knife bevel, that component remains constant. You can see this by looking at it perpendicular to the plane of the holder (end on) rather than perpendicular to the rod.
I'd say another reason for angle change when working towards the tip of the blade is the knife flexing. I've noticed this myself when working with longer chefs knife, too much pressure and the blade flexes a little, and this flattens the sharpening angle. Easily fixed by adjusting the clamping position of the knife to minimise flexing, and adjusting pressure appropriately.
I have held this incorrect belief for a longer time than I would like to admit. The solution is simple, which makes it a bit shameful to not get it right away. If I ever stopped to think about it and solved the problem, I would have gotten the answer but the human mind is lazy. This causes us to believe odd things that are obviously not true if you stop to think about them, but we seldom question our beliefs. I get into arguments to learn, not to win. I’m always relieved when proven wrong, because once I understand where I made a mistake, me being wrong is in the past. Thank you. This was the most valuable content I saw on RUclips in a long time. Comparable to getting the Monty Hall problem, which someone else mentioned as well.
These diskussions went on in the knife world back in the 1990’ties also, when guided sharpeners like Lansky was still relatively new. The roof example is great, i came to the same conklusions just by looking at the stone from the side.
Excellent presentation. Please correct me. On fixed sharpeners the stone is at the edge of the knife. When you apply downward pressure on the rod. Are you not creating a steeper angle on the edge of the blade? I think this is called the micro bevel or secondary bevel. This leads to the question how much of a secondary bevel do you need if any? And how do you measure and cheat a specific angle. Not 5 years old but may be dumb? 😊😊😊
Perfect explanation, i was trying to get my head around that for a long time now. I own way too many sharpening stones now. What I am now trying to figure out, how does this relate to the rolling sharpeners ("Horl") in relation to curved blades?
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Great explanation!
My roof is now hair whittling sharp.
Directions unclear, I sharpened my knife on the roof.
Directions VERY unclear. I sharpened my roof.
Don't trip on the roof dormer and fall into the skylight.
Turns out shingles are OK at sharpening 😅
Roof is a good blade steel 😅😂
Sharpened mine with a roof 😂
Dang, Alex. You just blew my mind. The roof example explained it really well, and proved to me that I was wrong.
We put out a sharpeners video earlier this year, and I took part in perpetuating the myth, saying that if your edge didn't fall along the perfect radius of the circle drawn by the sharpener, then you'd get uneven edges. The knife we sharpened for the demonstration did get uneven edges, but your video explained that nicely.
I think another thing I learned here is that, in addition to the knife maintaining the same edge along a straight line, the "perfect radius" thing I talked about in the sharpeners video also applies. So if you have a drop point that goes behind the "roof line" you showed us, the stone can still turn and give you a perfect angle along its radius.
As always, I learn a lot from your videos. Thanks for making them, and making all us knife nerds a little smarter every day. I hope to be proven wrong by many of your videos in the future!
-George
Hey buddy 😆 agreed 👍
I can't remember where i read the roof explanation, I think it was on a forum a long time ago, but that was the moment I realized, I was thinking about the angle from the wrong direction. It blew my mind when I heard it as well👍
@@OUTDOORS55You and Neeves are elevating the video standard on RUclips for knife sharpening videos. Before you two, this information was out there but it was really scattered and hard to piece together. I’ve really enjoyed being able to learn from the content that you two produce, which has enabled me to help my friends learn how to sharpen as well.
@@OUTDOORS55 I remember where you possibly saw it. It was a RUclips post by a knife maker who was sent a knife sharpener by the company to review it. And he gave the roof profile to explain the bevel angles. It was well before Covid so a fair while ago.
@@pinsquidHey. Yepper, you're so right! ✨😺
I don't care about knives. I don't care about sharp knives. I don't care about grinders.
Why can't I stop watching this guy's videos?
people love seeing professionals at work or just in general people in flow states. I also think that we as men just love getting shit right and appreciate a well explained deep dive into any sort of matter🤔
@@snowhusk
Knives are also one of those hobbies full of old wife's tales which are repeated as fact.
It's nice to see someone back up their claims with evidence, and refute the parroted misinformation.
@@JMMC1005 yup, totally agree with you! It's funny how even deep in the weeds we can still retain some of those myths, like with the topic of this video
And we've got a great community for that! This channel and Jerad from Neeves Knives are great for sharpening information (I still refer people to Jerad's video on pull-through sharpeners to explain why those don't work and why you wouldn't want them) and Pete from Cedric Ada is great for comparative tests and general no-bs view on knives (I studied his results of different steels' cut tests when I was getting back into the hobby, and now my daily drivers are either D2 or 14c28n, couldn't be happier on a budget and it's great to know exactly in which ways and how they are different to 8cr13mov, the defacto pocket knife budget steel for the original time period when I was into knives)
Nice explanation. When I saw your roof setup, I realized that I hadn't taken into account that the sharpening stone rotates so that it is always contacting the knife edge at the roof angle, not the rod angle.
Great explanation. I'm a mathematician, and I incorrectly assumed the angle was changing on long knives when I was using a fixed angle sharpener. The visual with the roof was brilliant. I didn't need to see any more to realize my mistake.
It was an ah hah moment for me as well👍🙂
I hope you don't teach math, because this is basic trig. 😅
@@benconstruct I take it you posted before watching the whole video?
A mathematician would do the math.... You seem to have stopped being a mathematician temporarily.
@@DreadX10 I mean, most people don't exactly tend to take their work home with them
"the only place these angle finders are accurate is when the guide rod is perfectly aligned with the center of the knife sharpener"
I NEEDED TO HEAR THIS! 😅
Thank you. 🍻🙌
Thanks.
As a retired engineer and (manual) draftsman, ia am well aware of the angles, however you have provided me with another way to attempt to explain this to laymen.
Now, back to my Laskey sharpener.
Mechanical Drafting is unfortunately soon to be a lost art/skill, at least in the field of architecture and similar design type fields of work. There was a really good article written a while ago by Michael Graves regarding how much the design field in total is going to suffer and things will become more and more sterile and similar looking as technology advances & it explains why so many commercial buildings are absolutely unremarkable while buildings designed 50-100 yrs ago have an inexplicable sense of character and beauty.
Did you explain that it is sweeping a conical surface and not a planar one, but that it doesn't matter? If not, then they are right and you are wrong... just not in any practical way.
What do I mean? Sweep the device 360 degree. Now tell me if you just defined a plane? The answer is no. You instead defined a cone.
@@krisspkriss I was kind of wondering why nobody was arguing this video is incorrect.
With a curved blade, so long as you clamp it at the same place each time, you’ll get the same angle at each point of the blade from sharpening to sharpening. That consistency is more important than the exact angle.
Visually it can be an issue though, almost all of my knife has a noticeably larger edge than the belly. Personally I do like the look but can see people would like a crisp, even edge
Thanks for the reminder. Symmetrical bevels is really what I'm after rather than a precise angle.
True. It will still have a slight difference in edge angles depending on how curved the blade is but realistically, those differences would be quite small and be inconsequential.
What you can do (and what i did at the beginning) is just draw a square along the clamp's edge on the blade for the first side so that when you flip it over, you can clamp it in the same spot. That's if it's one of the types that don't rotate 360 degrees and you need to remove the blade and flip it yourself, if not then there's no need for that.
Ótima explicação !
Yes- but the angle will be slightly different throughout the blade
Thanks for going over this. I started out with a fixed-angle sharpener from WorkSharp and have been wracking my brain over this "problem" since. I, too, am five years old.
Thank you for taking the time and having the initiative to teach us things like this. The roof analogy was perfect!
This is a great video and clears up one of the biggest misconceptions about fixed angle systems. Nice work!
The key takeaway here is that angle does change when there is a curvature, the difference on a fixed angle is so minimal, your free hand technique willdprobably deviate more. I have been using free hand and fixed angles for years and only use fixed for my expensive kitchen knives, it just gives so much control over the actual angle and never get any scratches. I mainly have 240mm japanese kitchen knives and both Shapton as Naniwa stones are available for these systems. Free hand sharpening is just more satisfying and gives you a more DIY achievement feeling.
This is a good plan for when I start a chef knife collection.
But I 100% agree that free hand is extremely satisfying and relaxing with the proper mindset.
Some people meditate, I free hand sharpen.
I have nice Japanese kitchen knives that I freehand sharpen-now that I’m good enough at sharpening that I don’t dull them instead. The sharpening itself is satisfying but using a really sharp and really well-made blade is true bliss. 😊
Make yourself a diy fixed angle sharpener to have the best of both worlds- perfect sharpening without scratches and accomplishment satisfaction
No one does this stuff like you! Always learn a ton while being entertained, KEEP IT COMING!!!
The best sharpening channel on YT
In my experience with a similar system, there was a difference in angle toward the curved tip, but not enough to be problematic on the blades I tested with. The system I used was much smaller, meant to be portable. The longer the swing arm is (further the pivot point) the less of a difference in the angle as the blade curves. So if it's a concern for you, buy a system with a long swing arm.
I only do freehand thanks to you Alex. Nothing beats the pains and pleasures of freehand sharpening.
I ALWAYS learn something from your videos. Thanks for taking the time.
There have been some videos from others that have countered his arguments on more than one occasion. I'm just saying, no ones always right. And I still enjoy watching him even so.
The roof model is a genius explanation. Incredibly complicated mathematics explained with two boards nailed together. Outstanding job.
To get the angle measured . . . Place the angle finder at 90º to the the blade. Great explanation !
He did.
Great explanation! My old buddy Ken Schwartz tried to explain this to people for many years and a lot of folks just don't get it. Our intuition is not reliable sometimes, and we need to try many methods to learn until we find one that clicks.
@robbabcock Ken was the man. The great Sensei of all things sharpening and micro abrasives. RIP Ken you are missed.
@@KMESharpeners A true Renaissance Man as well! He knowledge was so vast and varied. He was also a good dude, and greatly missed.
True! Conversely, the angle DOES change if the blade is curved, but it's usually not significant.
It does change, but the change is usually minimal compared to the amount of angle variation inherent to freehand sharpening.
I talked about this in the video 😉👍
@@OUTDOORS55 But is there any technique you can use to minimize angle change when targeting the curve, or is it something we just have to live with? Sounds like it might be better to clamp your knife closer to the tip/belly instead of right in the middle? Does twisting/rotating the rod do anything when approaching the belly? Still so many questions! Thanks for the great video, as always!
@@xyrojin89
It's the perpendicular distance between the guide rod support and the blade edge that matters.
The easiest workaround would be to do the blade in sections, reclamping to get the distance consistent as you go.
@@xyrojin89 Like JMMC1005 said; do the knife in (small) sections and confirm that the distance from the edge to the base of the vertical rod-support remains the same.
You can also mitigate the difference by clamping the knife in such a way that the edge is as far away from the vertical as you dare (minimal spine between the clamps). Or by extending the distance between the clamp and the base of the vertical rod-support.
Your clamp and the rod-support don't have to be in one piece like with all these sharpeners. You can clamp the vertical rod-support to a workbench and clamp the knife at the edge of the workbench. Now you are only limited by the length of your rod (which you can always extend).
By increasing this distance, you decrease the difference in angle.
Example: if your knife is 5 wide at the belly but only 4 at the heel & tip. Sharpening it with a 10 distance (between spine and vertical) means:
The belly get sharpened at ( 10 + 5 ) = 15 distance, while the heel & tip get sharpened at 14 distance. This is a difference of about 7%
If you extend the rod and place the vertical support farther away, say at 100, the numbers become:
Belly ( 100 + 5 ) = 105 versus ( 100 + 4) = 104 for the heel & tip. Now the difference is less than 1%.
So you would go from a 7% difference in angle along the blade to a 'less than 1%' difference in angle !
excellent explanation and demonstration!
Superb explanation of a difficult subject. Thanks Alex.
Beautifully illustrated. Especially when you used the digital angle finder and reminded us that it has to be perpendicular to the blade in order to be accurate. Very nicely done.
Literally just bought a KME and the same Klein angle cube you used in this video. Couldn’t figure out for the life of me why the cube was showing different angles depending on the position of the guide rod. It’s like you read my mind and made the exact video I needed, thank you!
I havent used fixed angle systems yet. I'm still enjoying free hand quite a bit but I'm sure I'll get some fixed system eventually and when I do I'm sure I'll come back to this video.
As always thanks for the great content.
Thanks for explaining this.
As a side note I just got a sharpall 300/1200 stone to sharpen my kitchen knives which have been very poorly treated. I had been using a pull through sharpener but wasn’t really happy with the results.
I have now dropped myself in to the deep end and doing free hand sharpening.
I have to say you make it look very easy. I just want to point out how much skill you have, that you can pass on the information and techniques in a way that makes it seem very accessible , but it is definitely a skill that requires time and repetition to get good results and your videos are a great foundation for helping others work to getting good results
Hang in there! I now have about 20 sharpenings under my belt with the Sharpal (the last two or three, with a leather strop and 1 micron gunnyjuice) I am still not getting "hair shaving" edges. But my knives are all much sharper than they were before. And I was able to get them sharp enough to make a very noticeable difference in use almost immediately.
The reason I quit using fixed clamp systems was exactly what you mentioned about getting fat bevels at the tip. I've got a lot of older knives that were sharp but had really ugly, wide tip bevels that I've fixed on the worksharp KO grinder or freehand. Great explanation.
OK wow! I went in thinking he has to be wrong but you are not. Thank you! I'm a visual person!
Well... I guess I'll stop worrying about this. My brain thanks you.
Nice explanation thanks! Even as a engineer, I always struggled with geometry!
Thanks for this. I have been through a lot of math classes and the like in my life, and I would have thought the angle changed. Amazing way of proving me wrong! Thanks again.
I have always wondered about this when using my sharpener but never really questioned it because my knives got sharp. This cleared everything up
"...explain this... as if we are all 5 years old here, because that's about how old I am in real life."😆
A+ for Show & Tell today. ⭐ Well done.
Great explanation, as always. I learned so much on tbis channel already. 😮
Thank you. I, too, always thought the angle changed along the knife, and I am now very happy to see I was wrong.
I believe some (not all) curves will work as well. For example, a centered, perfect circle should work! I _think_ it's just this needs to be satisfied:
d * cos(x) = r
Where r is basically the clamp arm's length, d is the distance from the tower to the point of the blade that's being sharpened, and x is an angle of _misalignment_ between the rod's angle and the blade's "cutting direction" at that point (which is 90 degrees from the edge direction). All of this is 2D, ignoring height (imagine a top-down view)
None of these curves are arcs of circle, except for one with radius exactly r, so there are constraints here. But I believe this may let you get some reflex curves (think karambit).
So it depends on the rod's pivot angle, rotation, and extension, plus the _edge's tangent at a particular point._ A _perfectly circular blade centered on the pivot axis_ (or any arc of this circle) is a special case where neither d nor x are changing. If you break up x so that x = y - t where y is the rod's angle and t is the cutting direction angle, then a straight blade would be a "special case" where t never changes, only d and y. But other constant-angle curves are possible as long as you adjust d and x (or d, y, and t) such that the changes in one cancel out changes in the other(s).
With this, even tantos could be positioned so that both edges could be sharpened to the same angle if you wanted to do that, but you'd have to position the tanto exactly correctly. The main edge would be mounted like normal, but you'd have to slide it to the left/right enough so that the line of the secondary edge, if extended, would be tangent to that imaginary circle. Basically, if you put the rod over the heel where the two edge meet, it'd need to exactly bisect it its angle; the two sides would be reflections of each other (across the rod).
This is because there are two ways for the rod angle and cutting direction to be off by x degrees -- clockwise, or counter-clockwise. So every point in space actually has two solutions (except the circle itself, which only has one everywhere on its edge. And I guess its very center). Another way of saying that is that cos(x) = y has two solutions for x: acos(r), and -acos(y).
So when designing an edge, you can continuously choose the angle that takes you away from the circle, until some point, then switch to choosing the angle which takes you towards the circle, and it can still maintain a constant angle the whole way. If the initial edge is straight, then this will result in tanto-like blades. For other angles/curves, both parts would be curved, but there's be a discontinuity at some point. Again, each side of the discontinuity would be a reflection of each other.
Also, although points exactly on the circle only have one solution, they have many possible "next" solutions. So you could have one side of the clamped point be one curve and the other side be another, breaking symmetry at that point.
For points inside the circle, going "away" from the circle means going to the center. Swapping to curve back towards the circle again would create another kind of "reflex" edge with a discontinuity inside it. "Normal" reflex edges might be possible by going to points further than needed for a straight line.
Excellent demonstration! The idea of looking at the sharpening stone on its slider from the side is very convincing. The demo with your roof model is even better.
In other words: The angle that matters is the bevel measured perpendicular to the edge.
I love your idea of using a 'roof' model!
BTW - in the demo of how blade sweep affects the angle, you rotated the sketch board in the wrong plane. A swept edge would remain in the same plane as the 'roof'. But, I understand what you were trying to say.
No it was the correct direction. The angle on the "sweep" changes based on blade length. Since the sweep rotates the angle to the angle of the guide rod, which changes based on length from the center. I just scratched the surface here and its hard to visualize haha
Bevel size change depending on the primary grind, multiple grind knives and spantos are notorious for them.
Yes multiple grinds are generally the worst offenders. Tantos come to mind, when the main grind is thinner than the tanto. 👍
@@OUTDOORS55 can you do a tanto sharpening video please and thank you.
Thanks so much!! This clears up the misconceptions that I had!!!
That makes a lot of sense. Longer kitchen knives still pose a problem with my kme because of the curved tip. The bevel there teens to always be bigger than on the straight portion of the blade.
Thanks so much for this. I've been confused by this for several months!
I've been trying to explain this to people for a long freaking time. The angle doesn't change until you come around a corner on a fixed angle system, like this.
I've always used a "self healing mat' under the base of the sharpener. I line up the back of the sharpeners base to a horizontal line & when I clamp a blade in, I make sure the majority of the straight portion of the blade edge is centered to the guide bar & even with a line on the mat. To me, this helps ensure that at least the straight part of the blade has an even bevel. The belly will always be at a higher angle, depending on how far it curves back towards the vertical plate that the guide bar is mounted in. THAT is the angle/area that is causing some FUBAR in peoples' minds, I think. That, and what you showed, the angle finder has to be perpendicular to the angle guide mounting plate for accuracy.
That's how I perceived these fixed angle sharpeners working. Education may help but just having a mechanical mind, a love of how things work & working with your hands is what 'figured' this out for me. Me, a guy with a grade 10 education & 146 IQ. (had to get tested for a job placement, job) I asked, "is that good?" lol
Thanks for the video & insight! Loved it.
Cheers
I never gave that any thought when i got mine, in the end my knife was sharp without much work
I'm glad you mentioned that angle can change with curved blades. To make it clear, If axis of the radius of the edge goes exactly through the heim joint of the sharpener, angle will not change. If that axis is behind the heim joint (big radius) angle will get lower as you go away from the center. If axis is between the edge and heim joint (agressive curve) angle will get higher as you go away from the center.
That guy needs a show on the discovery channel
Seems like the ability for the rod and stone to rotate freely in addition to pivoting and extending is key here. I hadn't considered that before, and because of that I had thought the angle wouldn't be consistent.
In fact, that extra degree of freedom makes me wonder if it might also give relatively consistent angles even for curved blades? Before you showed me this I thought it could only be consistent for a perfect circle centered on the pivoting axis (which would also imply the rod would never need to extend or retract). And without rotation I think that would be true. With rotation I think any shape between that circle and perfectly straight could work, i.e. a curve that's gentler than the circle would work, up to and including it being so "gentle" it's actually straight. A curve that's _tighter_ than that corresponding circle couldn't be perfectly consistent, but might at least be closer than you would expect. I don't think a reflex curve would be any better though.
Edit: Eh, I don't think just _any_ curve between the two would work, even if you considered local curvature. In the tanto scenario the tip area's edge is straight but could be farther away, which would be a different angle. Either perfectly straight and perfectly circular are the only optima, or else for every point between the two there's a unique blade direction that would work, but I'm not sure how you'd find it. Curves might still be a little closer to consistent then you'd naively expect though.
Edit 2: Maybe every circle larger than one centered on the pivot axis, positioned so the center is directly behind/in-line with the pivot axis and clamp would work. So any arc of a blade that follows the edge of one of these circles would work. If you position a blade to take advantage of this you'd get better consistency than otherwise. Maybe.
One way to visualise it is to look at the rod from the side, along the blade. That way you can see that the angle does not change as long as the blade edge is straight.
Well done, well explained
I am 66 and i learned something today thank you.
I will add this comment as a yes and... Long comment comming here. Sorry.
1. The knife edge has to be perfectly centered to the center line of the clamp or the angle of the stone to the edge will change back and forth every time you switch sides of the blade by rotating it. This has definitely been one of the more distinct challenges for me using the kme system but it will also reveal that not every Factory sends their knives out with a perfectly symmetrical on both sides of their knives. Cold Steel specifically has been pretty bad about this for me. To the point that some of their edges I.'d almost qualify as a chisel ground.
2. Because the KME uses and easily ratating single clamp the and because of the rubber lining of boot on the inside of the clamp, the firther from the center of the the clamp line the clamp. It os fairly easy to flex the out of alingment on both the rotating alignment and the clamp Center Line alignment. This is why it is very important to both have the clamp locked down very tight and the rotation set to a fairly tight lock in well. The more pressure added from the stone the easier it is to flex the knife. I used the term because it dosent so much shift because after the preasure is lifted it will retirn to where you had it set.
3. The actual number of the angle matter for f*** all in except to give you an idea of how thin or thick your edge will be.
4. The height/broadness of the blade (spine to edge) will effect the angle from one knife to the next if the angle height is unadjusted.
5. Running a fealty along the edge is the best method for checking that you are getting a good surface contact between the stone and the edge bevel. It is also good to recheck that you are continuing to get that perfect match throughout your sharpening. I have had it where I had everything perfectly aligned at the beginning of a sharpening session and then by the end I had pushed or changed the angle by over pressuring one side or the other of the knife in the clamp and it shifted. This left it so that I was too steep on one side and two shallow on the reverse.
6. I do think that the bigger the system the easier it is to sharpen across the entire Edge and look forward to getting the larger KME at some time in the future.
That's somewhat clearer. The 'roof angle' analogy is helpful. But then the belly and sweep muddied the waters. As a kitchen knife user and sharpener almost all our knives have bellies and sweeps.
Confusing, but good video! The bottom line is the exact angle is academic. What's important is the blade is sharp or the blade is not sharp.
You can just put your angle finder to the rod, move that rod to the end of the blade, and tun the angle finder to make it perpendicular to the blade to see the angle is the same. Maybe add small platform to the rod to make your demonstration simple.
I did this at the end of the video 👍
I have owned this style sharpener for years now and LOVE it. I had this discussion with a co-worker because everyone is a knife sharpening expert.
I think i need to draw it in CAD properly to show the sharpening angle. I did a basic one ages ago but mesured rod angle, it roughly shown a 2° change over a 6" blade centred in the clamp. But as you have shown, the stone rotates, and the sharpening angle is not the same as the rod angle.
With this system i only sharpen my 2x kitchen knifes once a year. No matience during that year only the sharpening
I see it now; the twist counteracts the pivot to maintain the angle.
You can apply the roof argument to a circular blade when you think of the roof as a cone with the pivot on its tip. Feels paradoxical until you really think about it.
That’s a good observation. You could sharpen a disc with a consistent angle all around if you put the pivot point on top of the center of the disc.
The straight roof becomes a traffic cone when you follow a positive curve.
@@Glocktologist Exactly. This means that it might pay off to think twice about were to clamp onto a curved knife.
so if you projected the triangle made by the sharpening arm onto a plane that was prependicular to the blade at any point it would be the same triangle. so the sharpening angle is the same at any point on a straight blade any distance from the pivot, but the sharpening angle changes if the blade curves?
Excellent explanation. In the beginning of the video I thought that finally I understand something better than Alex. But I stand corrected.
Baddass video man! I've been a knife nerd since I was a kid. Questions have been answered. Thank you
I was like "omg, the angle DOES CHANGE there aint NO way he can explain that"
Preceeds to do exactly that
I cant remember being mind blown like this since the Monty Hall problem
Thanks for the roof analogy. It really helps to understand.
To make it even more visual, you could attach a small laser pointer to the back end of the rod and project the beam onto a sheet or screen. When you sharpen the blade along its straight parts, the laser beam will follow a straight trajectory on the screen and along the curved parts of the blade, the beam will also have a curved trajectory.
Very nicely explained. Some folks like to obsess about it anyway, though. 🙂
Can you do a stropping material comparison video
Yeah, we imagine the angle in a 2D simplification and apply 2D knowledge of trigonometry to a 3D problem. The roof is an excellent non mathematical explanation! Good work!
This is a cool example of trying to apply a 3rd dimension to a 2D object. The reverse is also easy to demonstrate. The sharpener can be lifted and exist in a higher dimension than the plane. Adding curves makes more sense to our intuitive understanding of the world, where straight objects are always artificial.
This is the nice thing about free hand sharpening. If I ever feel I'm too shallow or too steep it's a pretty easy adjustment. It's relatively easy to adjust a mechanical sharpener too but it's hard to beat the convenience of your hands.
Wonderful explanation!!!! Love your stuff, man! 👍👍
good demonstration, just wondering if there is any noticeable difference with edge retention on these fix angles sharpened knifes.
I'm thinking the micro abrasion angles might not be diagonal with the edge. for example it looked like in your last video between 7-8 minutes you sharpened the knife near the center of the guide rod. It looks like there were times you are moving the stone perpendicular to the blade.
Does that affect the edge in any way, or does the strop afterwards fix that if it does?
I was wondering about the angle on a curved blade, as I use that same sharpener. Maybe call it a "consistent angle sharpener".
Roof example is excellent !!
Wow this is the best explanation of how this works. The simplicity which you have put this blows my mind. I knew that was a myth but I didn't have a good simple way of explaining it. Thank you
Great video and explanation Alex. Another way of visualising this is to place a light source at either end of the knife blade with the the light facing the sharpener side on. Turn of all other lights and project the shadow of the sharpening stone/arm on a wall. No matter where it is on the (straight) blade, the shadow will always show the same angle as you had set.
I think just filming along the line of the blade, would have done the job.
But the roof helps with the mental image.
Can't watch right now, so just passing by leaving a like and a comment to feed the algorithm. Have a good one guys
This is so much more simplified than I could have explained it and to try and explain it with maths we would have an hour long video, and half the viewers falling asleep during it bring back memories of college days
Brilliant, explains it perfectly.
Excellent....I did have a "Ha Ha" moment. Thanks. So what's your advice to novice knife sharpeners like me...use a fixed angle sharpener or learn to do it freehand?
At first i was worried that you misunderstood the problem, until you showed the "exception". (And i am really happy, because you explained the angle change there in a very visual way.)
But, in my opinion, the word exception is probably not the perfect fit, as most blades have a curve towards the tip. I don't have a single one that is comppletely straight, or has little to no belly towards the tip. More the opposite.
For example, if you look at a Kabar or a Glock field knife, and clamp it at close to the grip, the angle change is noticable with your eye. As like you mentioned, the bevel you create with the sharpening system widens. But if you clamp it closer to the tip, you can avoid thining out the tip.
I thought I couldn't be surprised by anything in the realm of sharpening anymore. Wrong I was! Good job.
I think the ”problem” people have is what you explain at 06:58
They see a difference in edge width and assume the angle has changed.
It’s the ‘lifting the elbow’ part on whetstones.
Thanks !!!!!
Thanks for the support 🙏
Amazing explanation! Beautiful simplicity
The angle changes only if the distance from the contact point of the stone to the knife to the pivot point gets closer. ie carve blade. easy way to tell is when the guide rod upwards or downwards. if you are sharpening a kukri for example.
Thank you for taking time to explain this. I have never seen a youtuber explaining this. i busted my brain thinking about this conundrum.
Great explaination, brain bender to imagine the contraints for wich fixed angle sharpeners keep blade angle constant. They clearly work with both straight knives and knifes with curvature where the sharpener pivot point is the center of curvature, probable also curvatures intermediate to this. However not knives where the curvature changes. so you will not be able to sharpen a kopesh on fixed angle sharpeners
Brilliant! Being able to transmit that “aha” moment. Priceless.
Excellent explanation. Those guys must be flat earthers...
Brilliant explanation
Bloody brilliant! Before the aha I really thought you were wrong. Within 2 seconds of seeing the roof it was so clear! Great explanation.
I knew when you posted the last video that inevitably this follow-up would be coming. It's crazy to me how many people needed to be spoon fed this. Doesn't seem that complex.
I've noticed in most fixed angle sharpeners, if the angle is changing much on longer blades, it's usually do to clamp rotation, or some other critical tolerance failing when you need it. Great follow up vid my mans.
It is a compound angle. There are two angles on two planes. The X Y plane and the ZY plane. The angle on the XY plane may change but it is the ZY angle that does not and that is the angle that is sharpening the blade. If you placed your camera parallel to the blade you can see the angle does not change and if you hold the angle meter perpendicular to the blade while the rod moved it should have stayed the same
Yes I do this at the end of this video 👍
Yes, if you treat it as vectors and resolve them to the plane of the knife bevel, that component remains constant.
You can see this by looking at it perpendicular to the plane of the holder (end on) rather than perpendicular to the rod.
I'd say another reason for angle change when working towards the tip of the blade is the knife flexing. I've noticed this myself when working with longer chefs knife, too much pressure and the blade flexes a little, and this flattens the sharpening angle. Easily fixed by adjusting the clamping position of the knife to minimise flexing, and adjusting pressure appropriately.
I have held this incorrect belief for a longer time than I would like to admit. The solution is simple, which makes it a bit shameful to not get it right away.
If I ever stopped to think about it and solved the problem, I would have gotten the answer but the human mind is lazy. This causes us to believe odd things that are obviously not true if you stop to think about them, but we seldom question our beliefs.
I get into arguments to learn, not to win. I’m always relieved when proven wrong, because once I understand where I made a mistake, me being wrong is in the past.
Thank you. This was the most valuable content I saw on RUclips in a long time. Comparable to getting the Monty Hall problem, which someone else mentioned as well.
Great explanation. You convinced me. Thanks!!!
Good explanation, thanks
These diskussions went on in the knife world back in the 1990’ties also, when guided sharpeners like Lansky was still relatively new. The roof example is great, i came to the same conklusions just by looking at the stone from the side.
Excellent presentation. Please correct me. On fixed sharpeners the stone is at the edge of the knife. When you apply downward pressure on the rod. Are you not creating a steeper angle on the edge of the blade? I think this is called the micro bevel or secondary bevel. This leads to the question how much of a secondary bevel do you need if any? And how do you measure and cheat a specific angle. Not 5 years old but may be dumb? 😊😊😊
Perfect explanation, i was trying to get my head around that for a long time now. I own way too many sharpening stones now. What I am now trying to figure out, how does this relate to the rolling sharpeners ("Horl") in relation to curved blades?